The question asks for valid implementations to export two functions, foo and bar.

Option A uses named exports, which is the standard way to export multiple, distinct functions or variables from a module. They are imported using the same names: import {foo, bar} from './utils.js';.

Option D uses a default export of an anonymous class. This class contains foo and bar as methods. This is a valid way to group and export related functionality. It would be imported and instantiated like: import MyUtils from './utils.js'; const utils = new MyUtils(); utils.foo();.

B. export default {foo, bar}; exports a single object as the default. While it works, named exports (A) or a class (D) are more conventional patterns for exporting distinct functions or a cohesive set of methods.

C. import {foo} from "./helpers/utils.js"; export {foo, bar}; is incorrect because it attempts to export bar without it being defined or imported in the module's scope, which would result in a reference error.

MDN Web Docs, export statement. The page details named exports (like option A) and default exports (like option D). See sections "Using named exports" and "Default exports".

Salesforce Lightning Web Components Dev Guide, "Share JavaScript Code". This guide illustrates the use of ES6 modules, showing examples of both named and default exports for sharing utility functions and classes.